A Spindt-type electrode and a carbon nanotube electrode (CNT) have been known as conventional electron emitting elements. Applications of such conventional electron emitting elements to, for example, the field of Field Emission Display (FED) have been studied. Such electron emitting elements are caused to emit electrons by tunnel effect resulting from formation of an intense electric field of approximately 1 GV/m that is produced by application of a voltage to a pointed section.
However, each of these two types of the electron emitting elements has an intense electric field in the vicinity of a surface of an electron emitting section. Accordingly, electrons emitted obtain a large amount of energy due to the electric field. This makes it easy to ionize gas molecules. However, cations generated in the ionization of the gas molecules are accelerated in a direction of a surface of the element due to the intense electric field and collide with the surface. This causes a problem of breakdown of the element due to sputtering. Further, ozone is generated before ions are generated, because oxygen in the atmosphere has dissociation energy that is lower than ionization energy. Ozone is harmful to human bodies, and oxidizes various substances because of its strong oxidizing power. This causes a problem in that members around the element are damaged. In order to prevent this problem, the members used around the electron emitting element are limited to members that have high resistance to ozone.
In order to solve this problem, an MIM (Metal Insulator Metal) type and an MIS (Metal Insulator Semiconductor) type have been known as other types of electron emitting elements. These electron emitting elements are surface-emission-type electron emitting elements which accelerate electrons by utilizing quantum size effect and an intense electric field in the element so that electrons are emitted from a flat surface of the element. These electron emitting elements do not require an intense electric field outside the elements, because the electrons which are accelerated in respective electron acceleration layers inside the elements are emitted to the outside. Therefore, each of the MIM type and the MIS type electron emitting elements can overcome the problems such that (i) the element is broken down by the sputtering which occurs due to ionization of gas molecules and (ii) ozone is generated, in the Spindt-type, CNT type, and BN type electron emitting elements.
For increasing mechanical strength of such electron emitting elements, for example, Patent Literature 1 discloses, as an electron acceleration layer, an electron emitting section and an insulating film configured by a powder layer made of a plurality of insulating material particles and an oxide insulator coating this powder layer. This insulating film is used as a spacer in a predetermined region on an electrode substrate. In the electron emitting element of Patent Literature 1, it is required to control film thicknesses of the electron acceleration layer and a thin-film electrode on the electron acceleration layer and to maintain mechanical strength.
Further, for example, Patent Literature 2 discloses an electron emitting element including, as an electron acceleration layer, a relatively thick insulating film containing metal or semiconductor fine particles. Regarding the electron emitting element of Patent Literature 2, it is reported that: because the fine particles are dispersed in the insulating film, a voltage of 10 V or more can be applied to the electron emitting element; dielectric breakdown of the insulating film becomes difficult to occur; and a process yield and reproducibility are improved.